Moon and Antares

You are missing some Flash content that should appear here! Perhaps your browser cannot display it, or maybe it did not initialize correctly.

Your browser does not support the html5 audio element.

Your browser does not support the html5 audio element.

On a human scale, the Moon is gigantic. It's more than 2,000 miles in diameter -- about a quarter the size of Earth. And it's a solid chunk of rock, so when you reach the surface, you hit it with a thump.

But on the astronomical scale, the Moon is little more than dust in the solar wind -- a mere speck of matter that hardly registers.

To understand just how tiny, consider its companion tonight: Antares, the brightest star of the constellation Scorpius, the scorpion. The bright orange star stands just to the left of the Moon as night falls.

Antares is one of the giants of the Milky Way galaxy -- it's far bigger, brighter, and heavier than all but a handful of the Milky Way's hundreds of billions of stars.

To get some idea of just how big it is, consider this: If the Moon were the size of a golf ball, Antares would be as wide as all of a golf course's holes laid end to end -- about four miles in diameter.

Unlike the Moon, though, you'd have a tough time knowing just when you arrived at Antares -- there's no solid surface. In fact, the gas at the star's visible surface is so thin that it's barely more than a vacuum. What's more, Antares blows a thick "wind" of gas into space, so there's not a sharp boundary between the star and space itself.

Yet Antares contains so much gas, spread over such a huge volume of space, that the star is one of the brightest in our night sky, even though it's about 550 light-years away.

Script by Damond Benningfield, Copyright 2010

Bookmark or share this page

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

Keywords

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.

Month (31 days), $8

Year, $30

Type:

New subscriber

Gift

Featured Images

Subscribe

+Get the ultimate StarDate fan experience with our new premium digital package — a one-year subscription to the digital edition of StarDate magazine and a one-year subscription to our same-day audio service. For a limited time, we're offering both together for just $45, a savings of 20% over purchasing both separately.